PC Engine/TurboGrafx-16

Known issues and quirks

Most consoles exhibit some degree of jailbars, but there is a simple mod to fix this.
Earlier models of PC Engine, TurboGrafx-16, and Duo systems are prone to capacitor failures. It is recommended to replace the electrolytic capacitors (particularly surface mount ones) on any Duo system.
A lot of the earlier consoles seem to be prone to noise/interference on the video lines. For RF-based systems like the TurboGrafx-16 and PC Engine, it may be better to stick with an external option like the dbGrafx Booster for video output. If you want to use a CD add-on, you could modify the Interface Unit (IFU) using one of the simpler mods since audio is already amplified. Systems that come with AV ports can use the simple mods as well and seem to exhibit less interference.

PCE/TG16 disassembly guide.
S-video mod for all systems. This isn’t very thoroughly documented, but it’s pretty simple. Additional information is available here.
RGB mod for RF-based systems (TurboGrafx-16 and original PC Engine).
RGB mod for systems with an AV-out jack (CoreGrafx, SuperGrafx, and Duo systems).
IFURGB adds RGB output to the Interface Unit (IFU).
TG16 region switch allows Hucards from Japan to be used on US TurboGrafx 16 systems.
Turbo Duo and PCE Duo region mod allows Hucards from US and Japan to be played on PC Engines and all Duo systems.
Jailbar fix
SSDS3 video fix for video noise issues.
SSDS3 audio fix for audio buzz issues.

Everdrive – flash cart from Krikzz.
PC Henshin is a universal modless region adapter that has been discontinued, but is open source.
dbGrafx Booster is an add-on that provides composite, s-video, and RGB output for all models with expansion ports, but it is discontinued. It was also sold by Stone Age Gamer as the Engine Block AV.